//go:build go1.18
// +build go1.18

package xhash

/*
From https://github.com/cespare/xxhash

Copyright (c) 2016 Caleb Spare

MIT License

Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:
The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/

import (
	"encoding/binary"
	"fmt"
	"hash/maphash"
	"math/bits"
	"reflect"
	"strconv"
	"unsafe"
)

const (
	// hash input allowed sizes
	byteSize = 1 << iota
	wordSize
	dwordSize
	qwordSize
	owordSize
)

const (
	prime1 uint64 = 11400714785074694791
	prime2 uint64 = 14029467366897019727
	prime3 uint64 = 1609587929392839161
	prime4 uint64 = 9650029242287828579
	prime5 uint64 = 2870177450012600261
)

const intSizeBytes = strconv.IntSize >> 3

var prime1v = prime1

// Hashable allowed map key types constraint
type Hashable interface {
	~int | ~int8 | ~int16 | ~int32 | ~int64 | ~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr |
		~float32 | ~float64 | ~string | ~complex64 | ~complex128
}

// GenHasher64 按数据类型生成哈希函数
// Ref: cespare/xxhash, smallnest/safemap, alphadose/haxmap, cornelk/hashmap
func GenHasher64[K comparable]() func(K) uint64 {
	hasher := GenHasher[K]()
	return func(k K) uint64 {
		return uint64(hasher(k))
	}
}

func GenSeedHasher64[K comparable]() func(maphash.Seed, K) uint64 {
	hasher := GenHasher[K]()
	return func(_ maphash.Seed, k K) uint64 {
		return uint64(hasher(k))
	}
}

func u64(b []byte) uint64 { return binary.LittleEndian.Uint64(b) }
func u32(b []byte) uint32 { return binary.LittleEndian.Uint32(b) }

func round(acc, input uint64) uint64 {
	acc += input * prime2
	acc = rol31(acc)
	acc *= prime1
	return acc
}

func mergeRound(acc, val uint64) uint64 {
	val = round(0, val)
	acc ^= val
	acc = acc*prime1 + prime4
	return acc
}

func rol1(x uint64) uint64  { return bits.RotateLeft64(x, 1) }
func rol7(x uint64) uint64  { return bits.RotateLeft64(x, 7) }
func rol11(x uint64) uint64 { return bits.RotateLeft64(x, 11) }
func rol12(x uint64) uint64 { return bits.RotateLeft64(x, 12) }
func rol18(x uint64) uint64 { return bits.RotateLeft64(x, 18) }
func rol23(x uint64) uint64 { return bits.RotateLeft64(x, 23) }
func rol27(x uint64) uint64 { return bits.RotateLeft64(x, 27) }
func rol31(x uint64) uint64 { return bits.RotateLeft64(x, 31) }

// xxHash implementation for known key type sizes, minimal with no branching
var (
	// byte hasher, key size -> 1 byte
	byteHasher = func(key uint8) uintptr {
		h := prime5 + 1
		h ^= uint64(key) * prime5
		h = bits.RotateLeft64(h, 11) * prime1
		h ^= h >> 33
		h *= prime2
		h ^= h >> 29
		h *= prime3
		h ^= h >> 32
		return uintptr(h)
	}

	// word hasher, key size -> 2 bytes
	wordHasher = func(key uint16) uintptr {
		h := prime5 + 2
		h ^= (uint64(key) & 0xff) * prime5
		h = bits.RotateLeft64(h, 11) * prime1
		h ^= ((uint64(key) >> 8) & 0xff) * prime5
		h = bits.RotateLeft64(h, 11) * prime1
		h ^= h >> 33
		h *= prime2
		h ^= h >> 29
		h *= prime3
		h ^= h >> 32
		return uintptr(h)
	}

	// dword hasher, key size -> 4 bytes
	dwordHasher = func(key uint32) uintptr {
		h := prime5 + 4
		h ^= uint64(key) * prime1
		h = bits.RotateLeft64(h, 23)*prime2 + prime3
		h ^= h >> 33
		h *= prime2
		h ^= h >> 29
		h *= prime3
		h ^= h >> 32
		return uintptr(h)
	}

	// qword hasher, key size -> 8 bytes
	qwordHasher = func(key uint64) uintptr {
		k1 := key * prime2
		k1 = bits.RotateLeft64(k1, 31)
		k1 *= prime1
		h := (prime5 + 8) ^ k1
		h = bits.RotateLeft64(h, 27)*prime1 + prime4
		h ^= h >> 33
		h *= prime2
		h ^= h >> 29
		h *= prime3
		h ^= h >> 32
		return uintptr(h)
	}

	float32Hasher = func(key float32) uintptr {
		k := *(*uint32)(unsafe.Pointer(&key))
		h := prime5 + 4
		h ^= uint64(k) * prime1
		h = bits.RotateLeft64(h, 23)*prime2 + prime3
		h ^= h >> 33
		h *= prime2
		h ^= h >> 29
		h *= prime3
		h ^= h >> 32
		return uintptr(h)
	}

	float64Hasher = func(key float64) uintptr {
		k := *(*uint64)(unsafe.Pointer(&key))
		h := prime5 + 4
		h ^= uint64(k) * prime1
		h = bits.RotateLeft64(h, 23)*prime2 + prime3
		h ^= h >> 33
		h *= prime2
		h ^= h >> 29
		h *= prime3
		h ^= h >> 32
		return uintptr(h)
	}
)

func GenHasher[K comparable]() func(K) uintptr {
	var hasher func(K) uintptr
	var key K
	kind := reflect.ValueOf(&key).Elem().Type().Kind()
	switch kind {
	case reflect.String:
		// use default xxHash algorithm for key of any size for golang string data type
		hasher = func(key K) uintptr {
			sh := (*reflect.StringHeader)(unsafe.Pointer(&key))
			b := unsafe.Slice((*byte)(unsafe.Pointer(sh.Data)), sh.Len)
			n := sh.Len
			var h uint64

			if n >= 32 {
				v1 := prime1v + prime2
				v2 := prime2
				v3 := uint64(0)
				v4 := -prime1v
				for len(b) >= 32 {
					v1 = round(v1, u64(b[0:8:len(b)]))
					v2 = round(v2, u64(b[8:16:len(b)]))
					v3 = round(v3, u64(b[16:24:len(b)]))
					v4 = round(v4, u64(b[24:32:len(b)]))
					b = b[32:len(b):len(b)]
				}
				h = rol1(v1) + rol7(v2) + rol12(v3) + rol18(v4)
				h = mergeRound(h, v1)
				h = mergeRound(h, v2)
				h = mergeRound(h, v3)
				h = mergeRound(h, v4)
			} else {
				h = prime5
			}

			h += uint64(n)

			i, end := 0, len(b)
			for ; i+8 <= end; i += 8 {
				k1 := round(0, u64(b[i:i+8:len(b)]))
				h ^= k1
				h = rol27(h)*prime1 + prime4
			}
			if i+4 <= end {
				h ^= uint64(u32(b[i:i+4:len(b)])) * prime1
				h = rol23(h)*prime2 + prime3
				i += 4
			}
			for ; i < end; i++ {
				h ^= uint64(b[i]) * prime5
				h = rol11(h) * prime1
			}

			h ^= h >> 33
			h *= prime2
			h ^= h >> 29
			h *= prime3
			h ^= h >> 32

			return uintptr(h)
		}
	case reflect.Int, reflect.Uint, reflect.Uintptr:
		switch intSizeBytes {
		case 2:
			// word hasher
			hasher = *(*func(K) uintptr)(unsafe.Pointer(&wordHasher))
		case 4:
			// Dword hasher
			hasher = *(*func(K) uintptr)(unsafe.Pointer(&dwordHasher))
		case 8:
			// Qword Hash
			hasher = *(*func(K) uintptr)(unsafe.Pointer(&qwordHasher))
		}
	case reflect.Int8, reflect.Uint8:
		// byte hasher
		hasher = *(*func(K) uintptr)(unsafe.Pointer(&byteHasher))
	case reflect.Int16, reflect.Uint16:
		// word hasher
		hasher = *(*func(K) uintptr)(unsafe.Pointer(&wordHasher))
	case reflect.Int32, reflect.Uint32:
		// Dword hasher
		hasher = *(*func(K) uintptr)(unsafe.Pointer(&dwordHasher))
	case reflect.Float32:
		hasher = *(*func(K) uintptr)(unsafe.Pointer(&float32Hasher))
	case reflect.Int64, reflect.Uint64:
		// Qword hasher
		hasher = *(*func(K) uintptr)(unsafe.Pointer(&qwordHasher))
	case reflect.Float64:
		hasher = *(*func(K) uintptr)(unsafe.Pointer(&float64Hasher))
	case reflect.Complex64:
		hasher = func(key K) uintptr {
			k := *(*uint64)(unsafe.Pointer(&key))
			h := prime5 + 4
			h ^= uint64(k) * prime1
			h = bits.RotateLeft64(h, 23)*prime2 + prime3
			h ^= h >> 33
			h *= prime2
			h ^= h >> 29
			h *= prime3
			h ^= h >> 32
			return uintptr(h)
		}
	case reflect.Complex128:
		// Oword hasher, key size -> 16 bytes
		hasher = func(key K) uintptr {
			b := *(*[owordSize]byte)(unsafe.Pointer(&key))
			h := prime5 + 16

			val := uint64(b[0]) | uint64(b[1])<<8 | uint64(b[2])<<16 | uint64(b[3])<<24 |
				uint64(b[4])<<32 | uint64(b[5])<<40 | uint64(b[6])<<48 | uint64(b[7])<<56

			k1 := val * prime2
			k1 = bits.RotateLeft64(k1, 31)
			k1 *= prime1

			h ^= k1
			h = bits.RotateLeft64(h, 27)*prime1 + prime4

			val = uint64(b[8]) | uint64(b[9])<<8 | uint64(b[10])<<16 | uint64(b[11])<<24 |
				uint64(b[12])<<32 | uint64(b[13])<<40 | uint64(b[14])<<48 | uint64(b[15])<<56

			k1 = val * prime2
			k1 = bits.RotateLeft64(k1, 31)
			k1 *= prime1

			h ^= k1
			h = bits.RotateLeft64(h, 27)*prime1 + prime4

			h ^= h >> 33
			h *= prime2
			h ^= h >> 29
			h *= prime3
			h ^= h >> 32

			return uintptr(h)
		}
	case reflect.Pointer:
		hasher = func(key K) uintptr {
			k := reflect.ValueOf(key).Pointer()
			switch intSizeBytes {
			case 2:
				return wordHasher(uint16(k))
			case 4:
				return dwordHasher(uint32(k))
			case 8:
				return qwordHasher(uint64(k))
			default:
				return uintptr(unsafe.Pointer(&key))
			}
		}
	default:
		panic(fmt.Errorf("unsupported key type %T of kind %v", key, kind))
	}

	return hasher
}
